Conventionally, various image recording materials have been used. Particularly in recent years, recording materials for forming a color image are the mainstream. As a system of recording a color image, the inkjet system, the thermal transfer system, the electrophotographic system, the transcription system using photosensitive materials, the printing system, systems using writing tools such as pen and the like have been actively utilized, and as a material for forming a color image, various coloring matters (dyes or pigments) are used. In addition, a color filter is used, with regard to displays, in LCDs (liquid crystal displays) or PDPs (plasma display panels), and with regard to photographing equipments, in electronic parts such as CCD (charge coupled device). And in order to reproduce a full color image on a display by using these color filters or in order to record a color image reproduced on a display, a coloring matter (dye and pigment) for 3 primary colors of so-called additive color process and subtractive color process are used. However, there is actually no coloring matter which has absorption characteristics providing a desired color reproduction area and can tolerate various use conditions, whereby improvement thereof is strongly required.
The inkjet recording method has been rapidly prevailing and further developing due to its low material cost, possibility of rapid recording, less noise in recording, easiness of color recording, and the like. The inkjet recording method includes the continuous system of continuously flying ink droplets and the on-demand system of flying ink droplets responding to an image information signal. In addition, the discharging system includes a system of discharging ink droplets by applying pressure with piezoelectric elements; a system of discharging ink droplets by generating bubbles in ink by heat; a system by using ultrasonic waves; a system of sucking and discharging ink droplets by electrostatic force; or the like. Examples of the ink suitable for such inkjet recording include water-based ink, oil-based inks, solid (melting-type) ink and the like.
The performance required for the coloring matter used in inks for inkjet recording includes good solubility or dispersibility in solvents; ability of high density recording; good hue; good fastness to light, heat and active gases (oxidizing gases such as NOx and ozone, and in addition, SOx and the like) in the environment; excellent durability against water and chemicals; good fixation to record-receiving materials resulting in no bleeding; excellent storage stability as an ink; no toxicity, and also inexpensive availability; and the like. In particular, a cyan coloring matter having a good cyan hue, allowing recorded matters with a high print density without causing bronze phenomenon, and being excellent fastnesses of recorded image, for example, light fastness (durability to light), ozone fastness (durability to ozone gas) and moisture fastness (durability under high humidity) is strongly desired.
Bronze phenomenon means a phenomenon where the coloring matter on the surface of the record-receiving material is in the state of metal fragments and glares due to coloring matter association, ink malabsorption or the like. When this phenomenon occurs, all of the glossiness, the print quality and the print density deteriorate. Particularly when a metal phthalocyanine-based dye is used as a coloring matter, bronze phenomenon often occurs as “red-bleeding phenomenon” on the part where printing with high concentration is performed. When bronze phenomenon occurs, the color balance of the whole image becomes inhomogeneous and the image quality is lowered, which is why a coloring matter causing no bronze phenomenon is required. In addition, many glossy papers are recently used as a recording medium having a texture close to a photo-like texture, while variations in glossiness are generated on the surface of recorded matter and image texture is significantly lost if bronze phenomenon occurs in images recorded on glossy paper. Also in this viewpoint, a coloring matter causing no bronze phenomenon is strongly required.
As a water-soluble cyan coloring matter used for cyan inks for inkjet recording, a phthalocyanine-based coloring matter and a triphenylmethane-based coloring matter are typical. The typical phthalocyanine-based coloring matter reported and used in the widest range includes phthalocyanine derivatives classified into the following A to H.
A: Known phthalocyanine-based coloring matter having a C.I. (color index) number such as Direct Blue 86, Direct Blue 87, Direct Blue 199, Acid Blue 249, Reactive Blue 71 or the like.
B: Phthalocyanine-based coloring matter described in Patent Literatures 1 to 3 and the like,
[for example, a mixture of Cu—Pc—(SO3Na)m(SO2NH2)n; m+n=1 to 4] (Cu—Pc-represents a copper phthalocyanine residue, —(SO3Na)m and (SO2NH2)n are its substituents, and m and n each represent a substitution number. Hereinafter, the similar description has the same meaning.).C: Phthalocyanine-based coloring matter described in Patent Literature 4 and the like,[for example, Cu—Pc—(CO2H)m(CONR1R2)n; m+n=a number of 0 to 4](R1R2 here represents a substituent such as alkyl. Hereinafter, the similar description has the same meaning.).D: Phthalocyanine-based coloring matter described in Patent Literature 5 and the like,[for example, Cu—Pc—(SO3H)m(SO2NR1R2)n; m+n=a number of 0 to 4, and m≠0].E: Phthalocyanine-based coloring matter described in Patent Literature 6 and the like, [for example, Cu—Pc—(SO3H)l(SO2NH2)m(SO2NR1R2)n; l+m+n=a number of 0 to 4].F: Phthalocyanine-based coloring matter described in Patent Literature 7 and the like, [for example, Cu—Pc—(SO2NR1R2)n: n=a number of 1 to 5].G: Phthalocyanine-based coloring matter described in Patent Literatures 8, 9 and 12 and the like,[phthalocyanine compound in which the substitution position of the substituent is controlled, phthalocyanine-based coloring matter in which a substituent is introduced at the beta-position].H: Benzo pyridoporphyrazine-based coloring matter having a 6-membered nitrogen-containing heteroaromatic ring such as a pyridine ring and a benzene ring, described in Patent Literatures 10, 13 to 17 and the like.
The phthalocyanine-based coloring matter typified by C.I. Direct Blue 86 or C.I. Direct Blue 199 which are usually used widely at present has a characteristic of being excellent in light fastness compared with magenta coloring matters and yellow coloring matters which are generally known. However, the phthalocyanine-based coloring matter has a greenish hue under acidic conditions, whereby it is not very preferable as a cyan ink. Therefore, it is preferred that these coloring matters are used under neutral to alkaline conditions when used as a cyan ink. However, although the ink to be used is neutral to alkaline, it is possible that the hue of a printed matter is greatly changed when the record-receiving material to be used is an acidic paper.
In addition, when the phthalocyanine-based coloring matter is used as a cyan ink, the hue of a printed matter is discolored greenish and also color fading occurs due to oxidizing gases such as nitrogen oxide gas and ozone which are often concerned nowadays as an environmental problem, whereby the print density is concurrently reduced.
On the other hand, the triphenylmethane-based coloring matter has a good hue but is very inferior in light fastness, ozone fastness and moisture fastness.
From here on, as the application field of inkjet recording is widespread and inkjet recording is widely used in articles on exhibition for advertisement and the like, there will be more opportunities for coloring matter and ink to be exposed to light and oxidizing gases in the environment. For this reason, coloring matter for inkjet recording will be more and more strongly required to have a good hue, to be inexpensive, and in addition, particularly to be excellent in various fastnesses as described above. However, it is said to be difficult to develop a cyan coloring matter (for example, phthalocyanine-based coloring matter) and a cyan ink satisfying these requirements at a high level. Also in the past, phthalocyanine-based coloring matters or benzo pyridoporphyrazine coloring matters to which fastness to ozone gases is imparted have been disclosed in Patent Literatures 3, 8 to 12 and 14 to 17. However, a cyan coloring matter which satisfies all the qualities such as hue, print density, light fastness, ozone gas fastness, moisture fastness and the like and causes no bronze phenomenon and further which can be inexpensively manufactured has yet to be obtained. Thus, the requirements of the market have not been sufficiently satisfied.